The invention relates to exhaust systems for marine propulsion devices and, more particularly, to means in such exhaust systems for relieving exhaust gas backpressure.
In prior marine propulsion devices, it is common to discharge exhaust gases and coolant water underwater in order to reduce noise. This frequently results in undesirable backpressure on the engine, because the exhaust gases and coolant water must follow a relatively long path before being discharged.
Attention is directed to the following U.S. patents which disclose marine propulsion device exhaust systems:
North; U.S. Pat. No. 3,759,041, issued Sept. 18, 1973; and
Harbert; U.S. Pat. No. 4,019,456, issued Apr. 26, 1977.